Embodiments of the invention are generally related to the field of radiation detectors, and more particularly, to a semiconductor crystal based radiation detector and a method of producing the detector.
Semiconductor crystal based radiation detectors are used for detecting ionizing radiation due to their ability to operate at room temperature, their small size and durability, and other features inherent in semiconductor crystals. Such detectors are used in a wide variety of applications, including medical diagnostic imaging, nuclear waste monitoring, industrial process monitoring, and space astronomy. Ionizing radiation includes both particulate radiation, such as alpha or beta particles, and electromagnetic radiation such as gamma or X-rays.
The semiconductor crystal based radiation detectors generally employ semiconductor materials, such as Cd—Zn—Te (CZT) which has a wide band-gap. A conventional CZT radiation detector typically comprises a CZT crystal located between a first and a second electrode. A bias voltage is formed across the electrodes by, for example, applying an external voltage from an external voltage source to at least one of the first and second electrodes. The bias voltage results in an electric field distribution in the radiation detector. One of the electrodes is a read-out electrode and is generally referred to as an anode electrode, and the other electrode is a cathode electrode.
Electron and hole pairs generated within the semiconductor crystal by an ionizing radiation adsorbed within the semiconductor crystal are separated, drift toward and collected by the anode and the cathode electrodes at external biases, respectively. These moving electron and holes create pulse signals in an external signal processing circuitry.
If all electrons and holes generated by the ionizing radiation are collected by the cathode and anode electrodes respectively, the output charge signal will exactly equal to the changes from the energy of the ionizing radiation deposited within the crystal. Because the deposited charge is directly proportional to the energy of the ionizing radiation, the semiconductor radiation detector provides a measurement of the energy of the ionizing radiation.
However, performance of the radiation detectors is typically limited by leakage currents which reduce the ability of the radiation detector to resolve the ionizing radiation. Accordingly, it is desirable to have an improved radiation detector with reduced leakage current, and a method of producing the radiation detector.